Generally, a light emitting device includes a package with an LED (Light Emitting Diode) mounted thereon and a lens for covering the LED for improving a light emission efficiency within a certain range of viewing angles. This lens may be produced in advance by casting or the like and then coupled on the package, but the lens and package are weakly adhered. Accordingly, a molding technique is used to form a lens-shaped molding member on a package with an epoxy or silicone resin.
A method of forming a molding member using resin is disclosed in U.S. Patent Publication No. 2003/0168720, by Kamada, entitled “Semiconductor Device and Manufacturing Method for same.” FIG. 1 is a sectional view illustrating a method of forming a molding member by Kamada.
Referring to FIG. 1, a metal plate is perforated to form a frame including metal leads (not shown), an air vent frame 303, and an injection frame 305, and a pressing process is performed to position ends of the metal leads below the frames 303 and 305, thereby completing the frame.
Then, a package support 304 (or a package body) is formed by injection molding. At this time, a heat sink 302 and the lead frame may be insertion-molded in a die to form the package body 304. The package body 304 has a recess exposing the ends of the metal leads and the heat sink 302 and has gates 306 adjacent to the frames 303 and 305.
Thereafter, an LED 301 is mounted on the heat sink 302 and is electrically connected to the metal leads through wire bonding.
Subsequently, a predetermined surface of an upper mold 401 is pressed to be adjacent to an upper surface of the package body 304. The upper mold 401 is shaped to have a trench for guiding a molding material to be injected, a trench for guiding gas, and recesses and protrusions for forming the molding member into a desired shape. The molding material flows to the gate 306 along the upper surface of the injection frame 305, and gas is discharged along the upper surface of the air vent frame 303 as being filled with the molding material. Accordingly, a space 403 is filled with the molding material, thereby forming a molding member with a desired shape. Meanwhile, a lower mold 402 having a recess receiving the package body 304 is pressed so that the entire package body 304 and the lead frame are in place.
According to the conventional method, there are advantages in that several molding members can be successively formed using a transfer molding method and resin burrs can be prevented by adopting the frames 303 and 305.
However, when the space 403 is filled with the molding material, the gate 306 at a side of the air vent frame 303 may be clogged with the molding material before the space 403 is completely filled with the molding material. Accordingly, the gas in the space 403 may not be discharged completely, but captured in the molding material. The gas captured in the molding material may cause inferior curing of the molding member and decrease uniformity and efficiency of the light emitted through the molding member.
An object of the present invention is to provide a mold capable of preventing gas from being captured in a molding material.
Another object of the present invention is to provide a method of forming a molding member, which can prevent gas from being captured in the molding material.
A further object of the present invention is to provide a method of forming a molding member, which can prevent burr from being generated.
In order to accomplish these objects, the present invention provides an improved mold for forming a molding member on a package, and a method of forming a molding member using the mold. In one aspect of the present invention, there is provided a mold including an upper surface; and a lower surface having an outer peripheral surface and a concave surface surrounded by the outer peripheral surface. Injection and discharge holes extend from the upper surface to the lower surface. Accordingly, after the mold and the package are coupled so that the discharge hole is directed upward, a molding material can be injected through the injection hole to form a molding member on the package, whereby it is possible to prevent air bubbles from being captured in the molding member.
The injection and discharge holes may extend from the upper surface to the outer peripheral surface of the lower surface. Accordingly, it may be prevented that the molding material contained in the injection and discharge holes is remained on the upper surface of the molding member with a desired shape.
In another aspect of the present invention, there is provided a method of forming a molding member. The method comprises preparing a mold including an upper surface, and a lower surface having an outer peripheral surface and a concave surface surrounded by the outer peripheral surface. The mold includes injection and discharge holes extending from the upper surface to the lower surface. In addition, a package having an LED mounted thereon is prepared. The package and the mold are coupled to each other. At this time, the package and the mold are coupled so that the concave surface covers the LED, the outer peripheral surface is adjacent to an upper surface of the package, an edge portion of the package adjacent to the discharge hole is directed upward, and an other edge portion opposite to the edge portion of the package is directed downward. Then, a molding material is injected into the injection hole. As the molding material is injected into the injection hole, a space between the concave surface and the upper surface of the package is filled with the molding material, and inner gas is discharged through the discharge hole. Since the discharge hole is positioned in an upper portion, the gas in the space can be discharged before the discharge hole is clogged with the molding material. Accordingly, it is prevented that the gas is captured in the molding material.
Meanwhile, the preparation of the package comprises preparing a lead frame having lead electrodes. The package body is formed on the lead frame. The package body has a recess exposing the lead electrodes. In addition, the lead electrodes protrude out of the package body. The LED is mounted in the recess region, and the LED is electrically connected with the lead electrodes.
The package body may have a guide groove for guiding the molding material injected through the injection hole toward the recess and a guide groove for guiding inner gas to the discharge hole. Accordingly, it is prevented that the molding material contained in the injection and discharge holes is remained on the upper surface of the molding member with a desired shape.
According to the present invention, it is possible to provide an improved mold capable of preventing gas from being captured in a molding material, and also to provide a method of forming a molding member capable of preventing gas from being captured in the molding material using the mold. In addition, the present invention may provide a method of forming a molding member capable of preventing resin burrs from being generated on lead electrodes.